Visualize fields on a latitude-longitude grid.

Install dependencies

First let's make sure we have all required packages installed.

using Pkg
pkg"add Oceananigans, CairoMakie, Imaginocean, GeoMakie"

Construct a test-bed field

Let's plot a field that lives on a latitude-longitude grid.

using Oceananigans

First create a latitude-longitude grid

Nx, Ny, Nz = 180, 120, 2

grid = LatitudeLongitudeGrid(size = (Nx, Ny, Nz),
                             latitude = (-60, 60),
                             longitude = (-155, 25),
                             z = (-1, 0),
                             topology = (Bounded, Bounded, Bounded))

180×120×2 LatitudeLongitudeGrid{Float64, Oceananigans.Grids.Bounded, Oceananigans.Grids.Bounded, Oceananigans.Grids.Bounded} on Oceananigans.Architectures.CPU with 3×3×3 halo and with precomputed metrics
├── longitude: Bounded  λ ∈ [-155.0, 25.0] regularly spaced with Δλ=1.0
├── latitude:  Bounded  φ ∈ [-60.0, 60.0]  regularly spaced with Δφ=1.0
└── z:         Bounded  z ∈ [-1.0, 0.0]    regularly spaced with Δz=0.5

Let's create a field. We choose a field that lives on the faces of the cells but any field should do.

We set the field value to $\sin^2(3λ) \sin(3φ)$ and see how that looks.

field = Field{Face, Face, Center}(grid)

set!(field, (λ, φ, z) -> sind(3λ)^2 * sind(3φ))

181×121×2 Field{Oceananigans.Grids.Face, Oceananigans.Grids.Face, Oceananigans.Grids.Center} on Oceananigans.Grids.LatitudeLongitudeGrid on Oceananigans.Architectures.CPU
├── grid: 180×120×2 LatitudeLongitudeGrid{Float64, Oceananigans.Grids.Bounded, Oceananigans.Grids.Bounded, Oceananigans.Grids.Bounded} on Oceananigans.Architectures.CPU with 3×3×3 halo and with precomputed metrics
├── boundary conditions: FieldBoundaryConditions
│   └── west: Nothing, east: Nothing, south: Nothing, north: Nothing, bottom: ZeroFlux, top: ZeroFlux, immersed: ZeroFlux
└── data: 187×127×8 OffsetArray(::Array{Float64, 3}, -2:184, -2:124, -2:5) with eltype Float64 with indices -2:184×-2:124×-2:5
    └── max=1.0, min=-1.0, mean=1.40974e-18

2D visualization

We can visualize this field in 2D using a heatmap. Imaginocean.jl adds a method to heatmap! so that it works with Oceananigans.jl fields.

using CairoMakie, Imaginocean

kwargs = (colorrange = (-1, 1), colormap = :balance)

fig = Figure()
ax = Axis(fig[1, 1],
          xlabel = "longitude [ᵒ]",
          ylabel = "latitude [ᵒ]",
          limits = ((-180, 180), (-90, 90)))

heatmap!(ax, field, 1; kwargs...)

fig

We can do the same but with a GeoAxis provided by the GeoMakie.jl package that allows us to easily add coastlines or also use various projections.

using GeoMakie

fig = Figure()
ax = GeoAxis(fig[1, 1],
             coastlines = true,
             lonlims = automatic)

heatmap!(ax, field, 1; kwargs...)

fig

3D visualization on the sphere

To make a 3D visualization on the sphere we first create a 3D axis and then use heatsphere! method from Imaginocean.jl.

fig = Figure()
ax = Axis3(fig[1, 1],
           aspect = (1, 1, 1),
           limits = ((-1, 1), (-1, 1), (-1, 1)))

heatsphere!(ax, field; kwargs...)
hidedecorations!(ax) # hides the axes labels

fig

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